Herpesvirus-6 (HHV-6) is a human pathogen that causes exanthem subitum (roseola) in children and appears to be associated with AIDS, tissue transplants and transplant rejection, various autoimmune diseases, lymphomas, Kaposi's sarcoma and other tumors, hepatitis, chronic fatigue syndrome, and several other diseases. Multiple strains of HHV-6 have been detected and categorized into two proposed groups. Unequivocal evidence is needed that HHV-6 is actually two or more closely related viruses, that each type is associated with different diseases, and that both types of HHV-6 can establish a latent infection in humans. The goal of the proposed research is to develop reagents for assessing various HHV-6 strains in clinical samples. We have recently developed a novel, high-throughput assay for distinguishing between different strains of virus by a single base pair resolution method. We propose to apply this assay to samples of HHV-6 amplified from clinical samples by use of the polymerase chain reaction (PCR) method. Products will be detected with chemiluminescent probes, which are as sensitive as p32-labelled probes and more sensitive than fluorescent ones. In Phase I, we plan to adapt these methods to a rapid, economical assay for screening the two major strains of HHV-6 in clinical samples. In Phase II, we will refine and extend these procedures for distinguishing among the subtypes of HHV-6 that have been detected in infected clinical specimens of blood, saliva, urine, and tissue.